1. Field of the Invention
The field of art to which this invention pertains is solid-bed adsorptive separation. More specifically, the invention relates to an improvement to an adsorbent, and an improved process for separating a component from a mixture comprising an aqueous solution of a mixture of different components which process employs an adsorbent comprising a crystalline aluminosilicate which selectively adsorbs a component from the feed mixture.
2. Prior Art
It is known in the separation art that certain crystalline aluminosilicates referred to as zeolites can be used in the separation of a component from an aqueous solution of a mixture of different components. For example, adsorbents comprising crystalline aluminosilicate are used in the method described in U.S. Pat. No. 4,014,711 to separate fructose from a mixture of sugars in aqueous solution including fructose and glucose.
It is also known that crystalline aluminosilicates or zeolites are used in adsorption processing in the form of agglomerates having high physical strength and attrition resistance. Methods for forming the crystalline powders into such agglomerates include the addition of an inorganic binder, generally a clay comprising silicon dioxide and aluminum oxide to the high purity zeolite powder in wet mixture. The blended clay zeolite mixture is extruded into cylindrical type pellets or formed into beads which are subsequently calcined in order to convert the clay to an amorphous binder of considerable mechanical strength. As binders, clays of the kaolin type are generally used.
Zeolite crystal and inorganic binder agglomerates have long been known to have the property of gradually disintegrating as a result of continuous contact with water. This disintegration has been observed as a silicon presence or contamination in the solution in contact with the adsorbent. Such contamination may at times be sufficiently severe to impart a cloudy appearance to the solution.
It has been discovered that the disintegration of the adsorbent may be minimized by substituting a water permeable organic polymer for the inorganic binder material. The adsorbent is made by mixing together a powder of the zeolite crystal, a powder of the polymer and a liquid organic solvent to form a malleable mixture. The mixture is then formed into discrete formations and dried.
We have discovered an improvement to an adsorbent having a water permeable organic polymer binder which enables even further reduction of its extent of disintegration in aqueous service.